Ornithological Mystery: Yellow Northern Flickers Turning Red

Hudon and his colleagues used spectrophotometry and chromatography to show that rhodoxanthin, rather than the type of carotenoid pigment that colors western red-shafted birds, was present in the feathers of yellow-shafted flicker specimens with the aberrant red coloration. Data from a bird-banding station helped confirm that the birds acquire the red pigment during their fall molt about early August, which coincides with the availability of ripe honeysuckle berries. The honeysuckles have also been implicated as the source of unusual orange feathers in Cedar Waxwings.

“At one point considered valuable wildlife habitat and widely disseminated, the naturalized Asian bush honeysuckles are now considered invasive and undesirable in many states. This is clearly not the last we have heard of aberrantly colored birds,” says Hudon. “The ready availability of a pigment that can alter the coloration of birds with carotenoids in their plumages could have major implications for mate selection if plumage coloration no longer signaled a bird’s body condition.”

“This is the pinnacle of a lengthy series of papers on the pigments deposited in primary feathers. Hudon et al. make use of the most up-to-date spectrometric and biochemical analyses to identify and quantify the pigments,” according to Alan Brush, an expert on feather color and retired University of Connecticut professor who was not involved with the study. 

“In addition to demonstrating that the red pigments in the molting yellow-shafted feathers are derived from their diets, not the result of interbreeding with the red-shafted form, they illuminate the dynamic nature of pigment deposition during molt, an accomplishment in itself.”

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